**8.3 What is the optimal method of screening for GDM?**


criteria are: This category of women needs to be screened at first antenatal visit and repeat at 24–28 week if they were negative at early screening. Women with these

g. Clinical conditions associated with insulin resistance like PCOS, acanthosis nigricans

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation…*

The most common method of screening is with stepwise 50 g OGTT at 24 to 28 weeks of gestation, followed by an OGTT as the diagnostic test if a certain threshold has been surpassed. The procedure for glucose challenge test (GCT), is that 50 g anhydrous glucose load dissolve in 150 ml fluid to be ingested within 5 minutes irrespective of time of the day or last meal. Blood is collected 1-hr post ingestion of glucose solution Views diverge on the optimal cutoff value for the 50 g GCT. 90% of women with GDM will be identified if 7.2 mmol/L (130 mg/dl) is used, however, as high as 20–25% of those screened will to undergo 100 g OGTT for diagnosis. Increasing the cutoff value to 7.8 mmol/L (140 mg/dl) will identify only 80% of women with GDM but decrease to 14–18% of women will do 100 g diagnostic

testing [97]. A cutoff value of 7.2 mmol/L is advice in those with FPG level is

<140 mg/dl (<7.8 mmol/L) and manifests symptoms compatible with complications of diabetes. Finally, at 24 to 28 weeks of gestation, every women should undergo 50 g challenge test and those with values between 7.2 to 7.8 mmol/L (130–140 mg/dl) should proceed to 100 g OGTT for diagnosis of GDM and sampling over 3-hrs.

As women with negative GCT do not undergo the diagnostic OGTT, it is possible that they could have undiagnosed GDM or GIGT. In a study involving 202 pregnant women with a negative GCT screening test that underwent subsequent OGTT, the only positive predictor noted is the average glucose value in those with normal and those with GDM/GIGT. Therefore, false negative GCTs cannot be readily predicted by risk factors. However, their clinical implications at delivery may be benign [98]**.** During pregnancy, some women have a low glucose level on the 75 g OGTT. These women tend to have more booking weight and higher rate of congenital anomaly; however their pregnancy outcome was shown not to be significantly different from those with normal screening OGTT results [99]**.** The performance of the GCT as a screening test depends on the cutoff values used, the criteria for diagnosis of GDM and the prevalence of GDM in the screened population. A study conducted in China where 422 gravidas [100] were screened with 50-g glucose and those with a positive results (≥135 mg/dl (7.5 mmol/L)), underwent additional glucose testing. GDM was defined using National Diabetes Data Group (NDDG) standards for the 3-h GTT. When Carpenter and Coustan was used for comparison, any woman with elevated 50-g value and no 3-hr OGTT was performed, a fasting serum glucose ≥140 mg/dl (7.8 mmol/L) were considered evidence of gestational diabetes. One hundred twenty four (29.4%) had GDM as defined by the NDDG criteria; this increased to 161 (38%) when the diagnosis was based on Carpenter and Coustan's criteria. As expected, the prevalence of GDM increased in relation to an increasing 50-g value. All subjects with a 50-g screen >216 mg/dl (>12.0 mmol/L) had evidence of gestational diabetes and required insulin for glycemic control. Patients with a 50-g screen ≥220 mg/dl (12.2 mmol/L) do not require a 3-h GTT. Those with fasting serum

features are categorized as high-risk [95, 96] (**Table 9**).

a. Obesity(BMI ≥ 30 kg/m<sup>2</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.96549*

*Feature indicators of women at high-risk for GDM.*

c. Previous GDM

**Table 9.**

**135**

b. Previous macrosomic baby weighing ≥4.5 kg

d. Glucosuria(1+ on two occasion or 2+ on one occasion) e. Family history of T2DM(first degree relative with T2DM) f. Ethnic family origin with a high prevalence of DM

h. History of hypertension or hypercholesterolaemia


Routine screening of women at 24–28 weeks of gestation may be recommended with 50 g glucose challenge test (GCT), using a threshold of 7.8 mmol/L (140 mg/ dl), except in those who fulfill the criteria for low risk and may not need screening for GDM at all. Properties used in categorizing a woman to at low-risk are [95, 96] (**Table 8**).

Women at moderate risk: women who do not meet all low risk criteria but lack two or more risk factors for GDM. Average-risk patients (all patients who fall between low and high risk) should be tested at 24–28 weeks of gestation. High risk


a. Caucasian or member of other ethnic group with low prevalence of diabetes

b. Pregnancy with body mass index(BMI) ≤27 kg/m2

c. No previous history of GDM or glucose intolerance or adverse pregnancy outcome associated with GDM

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation… DOI: http://dx.doi.org/10.5772/intechopen.96549*

a. Obesity(BMI ≥ 30 kg/m<sup>2</sup>


#### **Table 9.**

**8.3 What is the optimal method of screening for GDM?**

*Type 2 Diabetes - From Pathophysiology to Cyber Systems*

risk factor based [96].

income nations

are negative

(**Table 8**).

**Table 8.** *Low-risk group.*

**134**

with GDM

using this approach.

perform a 50 g glucose challenge test.

screened in the presence of maternal risk factors.

b. Pregnancy with body mass index(BMI) ≤27 kg/m2

d. No family history of diabetes in first-degree relative e. No history of GDM-associated adverse pregnancy outcome

a. The optimal method of screening for GDM depends on the location, the strength of the health facility, the principle of practicing Physician and affordability of the patients. Screening is therefore either universal based or

b. In order to reduce the burden of screening on women and the health care system, the concept of selective (risk factor based) screening was introduced.

c. The goal of risk factor based screening would be to ideally identify through historical and clinical factors those patients who would benefit most from biochemical screening while allowing those at lower risk to avoid the screening processes. This is preferred particular in the low-income and mid-

d. Selective screening originally consisted of taking a personal and family

e. High risk women should undergo diagnostic test as early in pregnancy as possible and that testing should be repeated at 24–28 weeks if initial results

f. Screening by risk factors alone has a sensitivity of 63% and a specificity of 56%. In other words, 37–50% of women with GDM may go undiagnosed

g. Hence universal screening was considered and is widely practices. Universal screening for GDM is practiced by 84% of Canadian obstetricians, 94–97% of US obstetricians; however in recent survey only 17% of physicians in the UK practiced universal screening while 11% did not screen for GDM and 72%

Routine screening of women at 24–28 weeks of gestation may be recommended with 50 g glucose challenge test (GCT), using a threshold of 7.8 mmol/L (140 mg/ dl), except in those who fulfill the criteria for low risk and may not need screening for GDM at all. Properties used in categorizing a woman to at low-risk are [95, 96]

Women at moderate risk: women who do not meet all low risk criteria but lack

c. No previous history of GDM or glucose intolerance or adverse pregnancy outcome associated

two or more risk factors for GDM. Average-risk patients (all patients who fall between low and high risk) should be tested at 24–28 weeks of gestation. High risk

a. Caucasian or member of other ethnic group with low prevalence of diabetes

history in order to identify a high-risk population in need of further directed testing. With this method, women are categorized into low-risk, moderaterisk and high-risk. Women with any of the risk factors below were advised to *Feature indicators of women at high-risk for GDM.*

criteria are: This category of women needs to be screened at first antenatal visit and repeat at 24–28 week if they were negative at early screening. Women with these features are categorized as high-risk [95, 96] (**Table 9**).

The most common method of screening is with stepwise 50 g OGTT at 24 to 28 weeks of gestation, followed by an OGTT as the diagnostic test if a certain threshold has been surpassed. The procedure for glucose challenge test (GCT), is that 50 g anhydrous glucose load dissolve in 150 ml fluid to be ingested within 5 minutes irrespective of time of the day or last meal. Blood is collected 1-hr post ingestion of glucose solution Views diverge on the optimal cutoff value for the 50 g GCT. 90% of women with GDM will be identified if 7.2 mmol/L (130 mg/dl) is used, however, as high as 20–25% of those screened will to undergo 100 g OGTT for diagnosis. Increasing the cutoff value to 7.8 mmol/L (140 mg/dl) will identify only 80% of women with GDM but decrease to 14–18% of women will do 100 g diagnostic testing [97]. A cutoff value of 7.2 mmol/L is advice in those with FPG level is <140 mg/dl (<7.8 mmol/L) and manifests symptoms compatible with complications of diabetes. Finally, at 24 to 28 weeks of gestation, every women should undergo 50 g challenge test and those with values between 7.2 to 7.8 mmol/L (130–140 mg/dl) should proceed to 100 g OGTT for diagnosis of GDM and sampling over 3-hrs.

As women with negative GCT do not undergo the diagnostic OGTT, it is possible that they could have undiagnosed GDM or GIGT. In a study involving 202 pregnant women with a negative GCT screening test that underwent subsequent OGTT, the only positive predictor noted is the average glucose value in those with normal and those with GDM/GIGT. Therefore, false negative GCTs cannot be readily predicted by risk factors. However, their clinical implications at delivery may be benign [98]**.** During pregnancy, some women have a low glucose level on the 75 g OGTT. These women tend to have more booking weight and higher rate of congenital anomaly; however their pregnancy outcome was shown not to be significantly different from those with normal screening OGTT results [99]**.** The performance of the GCT as a screening test depends on the cutoff values used, the criteria for diagnosis of GDM and the prevalence of GDM in the screened population. A study conducted in China where 422 gravidas [100] were screened with 50-g glucose and those with a positive results (≥135 mg/dl (7.5 mmol/L)), underwent additional glucose testing. GDM was defined using National Diabetes Data Group (NDDG) standards for the 3-h GTT. When Carpenter and Coustan was used for comparison, any woman with elevated 50-g value and no 3-hr OGTT was performed, a fasting serum glucose ≥140 mg/dl (7.8 mmol/L) were considered evidence of gestational diabetes. One hundred twenty four (29.4%) had GDM as defined by the NDDG criteria; this increased to 161 (38%) when the diagnosis was based on Carpenter and Coustan's criteria. As expected, the prevalence of GDM increased in relation to an increasing 50-g value. All subjects with a 50-g screen >216 mg/dl (>12.0 mmol/L) had evidence of gestational diabetes and required insulin for glycemic control. Patients with a 50-g screen ≥220 mg/dl (12.2 mmol/L) do not require a 3-h GTT. Those with fasting serum


#### **Table 10.**

*Indications for OGTT in pregnancy [101].*

glucose of ≥140 mg/dl (7.8 mmol/L) may begin diet therapy, glucose monitoring, and insulin as indicated. If the fasting serum glucose is <140 mg/dl (7.8 mmol/L), a 3-h GTT should be performed for confirmation of GDM. This approach will facilitate rapid therapeutic intervention and reduce the cost of care in this subset of patients. This findings need to be validated at different places using different ethnic groups. What should be considered an indication for screening for gestation diabetes mellitus (GDM) (**Table 10**).

[105], ADA [106], as the standard method for diagnosis of GDM for more than two

outcomes even in those with mild hyperglycaemia which did not meet the old criteria of GDM [107]. Based on this notion the International Association of Diabetes and Pregnancy Study Group (IADPSG) recommended a one-step 75 g OGTT testing but lowered the diagnostic cut-point of the OGTT to (5.1–10.0-8.5 mmol/L, fasting, 1-hour and 2 hours postprandial) in 2010 [108] and only one abnormal value was enough to make a diagnosis. This was adopted by ADA [109], WHO [110] and FIGO [111] by recommending a one-step 75 g glucose OGTT between 24 and 28 gestational weeks and diagnosis of GDM is made with only one abnormal value equal to or exceeding 5.1–10.0-8.5 mmol/L, due to the result of the HAPO study regarding mild hyperglycaemia and adverse clinical outcome, including LGA, primary caesarean, clinical neonatal hypoglycaemia, and C-protein cord blood [108] where a more strict strategy may help reduce the frequency of these potential complications. However, several guidelines including the ACOG [112], NIH [113] and SOGC [114] did not support the IADPSG criteria and their guidelines still recommend the two-step strategy and the C-C or NDDG criteria for the OGTT, the

a. The GTT is considered the most effective way to determine if you have GDM b. Early detection of GDM gives a better chance of monitoring glucose levels

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation…*

d. Managing the glucose levels early decreases the chances of macrosomic baby and its

e. Managing glucose levels decreases the risk of interventions in labour and delivery

c. Managing glucose levels early decreases the risks to the baby

In 2008, the HAPO study [39] demonstrated presence of unfavourable neonatal

a. The benefit from the treatment of mild GDM in women is not well established

d. Life disruptions and psychosocial burdens will be developed in a patients with

Current ADA guidelines recommended selective screening of high risk women for GDM, where ACOG guideline advice universal screening and NICE guideline recommended screening all women of South Asians ethnicity. In the HAPO study risk of adverse outcomes were very low when FPG was ≤4.4 mmol/L (80 mg/dl). In Chinese women with FPG value ≥5.1 mmol/L, one can make a diagnosis of GDM (specificity 100% and, in those with value ≤4.4 mmol/L one can exclude GDM (87.8%, sensitivity). These results are similar to those reported by Agarwal, et al. in the HAPO cohort. In HAPO and two other studies, the incidence of selected adverse maternal and fetal outcomes increases along a continuum of increasing maternal hyperglycaemia, with no outcome-associated glycaemic thresholds were identified that could be used to define internationally accepted criteria for the diagnosis of GDM. In 2010, IADPSG [108] consensus panel using HAPO study primary outcomes (birthweight >90%, primary caesarean section rate, neonatal hypoglycaemia and cord C-peptide levels >90%) and threshold for 75-g OGTT

b. Additional healthcare costs will be generated by increased prevalence

c. Caesarean delivery and intensive newborn assessment will increase

decades.

**Table 12.**

complications

*Advantages of OGTT for a pregnant woman.*

*DOI: http://dx.doi.org/10.5772/intechopen.96549*

reasons provided are:

GDM

**137**

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women of reproductive-aged and is the most common endocrine-associated cause of infertility. Approximately 6.5% of women of reproductive age have PCOS. Women with PCOS are known to be at increased risk for IR, IGT, and type 2 diabetes mellitus though often present with normal FPG [102]. The current guideline of Androgen Excess Society is that a 2-hour OGTT be performed on all obese women with PCOS [102]. Though screening for GDM is considered compulsory in affluent countries and highly recommended in low- and middle-income countries, the administering the required amount of glucose in pregnancy is not without side effects. The recognised disadvantages are as noted in **Table 11**, ranging from mild to moderate consequences.

However, advantage almost always surpasses the disadvantages. The advantages are as shown in **Table 12**.

#### **8.4 Diagnosis of GDM is only done using OGTT**

The gold standard for the diagnosis of GDM is OGTT irrespective of how it is performed, using 100 g as recommended by ACOG, or 75 g, according to the ADA criteria.

In 1964, O'Sullivan and Mahan first developed the two-step method OGTT for the diagnosis of GDM [103] and this is based on the risk of maternal type 2 diabetes later in life [104]. As explained earlier, those with glucose levels meeting screening limit undergo a 100 g, 3 hours or 75 g, 2-hour diagnostic OGTT and by Carpenter and Coustan (C-C) criteria, GDM is diagnosed in women with two or more abnormal values (5.3–10.0-8.6 mmol/L at fasting, 1-hr and 3-hour (2 hour) post glucose [104]. This with some modifications was adapted by many organizations, NDDG

**Table 11.** *Disadvantages of the OGTT in a pregnant woman.*

<sup>1.</sup> There are no serious direct risks to the GTT, however, some women reported dizziness, fainting, vomiting, due to fasting and/or the use of a high glucose drink on an empty stomach

<sup>2.</sup> Fasting for 8–12 hrs in pregnancy can be difficult

<sup>3.</sup> Soreness, bruise, swelling or infection at site of needle insertion

<sup>4.</sup>More cost burden in a patient with positive or borderline result who has be closely monitor

<sup>5.</sup> Patient may not be eligible for midwifery led care options such as homebirth or MLU

<sup>6.</sup> Induction of delivery may be recommended before date is due


#### **Table 12.**

glucose of ≥140 mg/dl (7.8 mmol/L) may begin diet therapy, glucose monitoring, and insulin as indicated. If the fasting serum glucose is <140 mg/dl (7.8 mmol/L), a 3-h GTT should be performed for confirmation of GDM. This approach will facilitate rapid therapeutic intervention and reduce the cost of care in this subset of patients. This findings need to be validated at different places using different ethnic groups. What should be considered an indication for screening for gestation

h. A family history of diabetes (first degree

k. Women with PCOS (Polycystic ovary

relatives) i. A previous still-birth j. Long usage of steroids

syndrome) l. Polyhydramnios m. High risk ethnic groups

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women of reproductive-aged and is the most common endocrine-associated cause of infertility. Approximately 6.5% of women of reproductive age have PCOS. Women with PCOS are known to be at increased risk for IR, IGT, and type 2 diabetes mellitus though often present with normal FPG [102]. The current guideline of Androgen Excess Society is that a 2-hour OGTT be performed on all obese women with PCOS [102]. Though screening for GDM is considered compulsory in affluent countries and highly recommended in low- and middle-income countries, the administering the required amount of glucose in pregnancy is not without side effects. The recognised disadvantages are as noted in **Table 11**, ranging from mild to

However, advantage almost always surpasses the disadvantages. The advantages

The gold standard for the diagnosis of GDM is OGTT irrespective of how it is performed, using 100 g as recommended by ACOG, or 75 g, according to the ADA

In 1964, O'Sullivan and Mahan first developed the two-step method OGTT for the diagnosis of GDM [103] and this is based on the risk of maternal type 2 diabetes later in life [104]. As explained earlier, those with glucose levels meeting screening limit undergo a 100 g, 3 hours or 75 g, 2-hour diagnostic OGTT and by Carpenter and Coustan (C-C) criteria, GDM is diagnosed in women with two or more abnormal values (5.3–10.0-8.6 mmol/L at fasting, 1-hr and 3-hour (2 hour) post glucose [104]. This with some modifications was adapted by many organizations, NDDG

1. There are no serious direct risks to the GTT, however, some women reported dizziness, fainting, vomiting, due to fasting and/or the use of a high glucose drink on an empty stomach

4.More cost burden in a patient with positive or borderline result who has be closely monitor 5. Patient may not be eligible for midwifery led care options such as homebirth or MLU

diabetes mellitus (GDM) (**Table 10**).

a. Previous pregnancy with gestational diabetes b. Previous 'big' baby (at or over 4.5kgs – 10lbs) c. Frequent loss of pregnancy or premature delivery

e. Positive glycosuria(1+ on 2 occasions or 2 + on one

*Type 2 Diabetes - From Pathophysiology to Cyber Systems*

d. Large for gestational age

g. Maternal age ≥ 40 years old

*Indications for OGTT in pregnancy [101].*

occasion) f. BMI ≥30 kg/m<sup>2</sup>

**Table 10.**

moderate consequences.

are as shown in **Table 12**.

criteria.

**Table 11.**

**136**

**8.4 Diagnosis of GDM is only done using OGTT**

2. Fasting for 8–12 hrs in pregnancy can be difficult

*Disadvantages of the OGTT in a pregnant woman.*

3. Soreness, bruise, swelling or infection at site of needle insertion

6. Induction of delivery may be recommended before date is due

*Advantages of OGTT for a pregnant woman.*

[105], ADA [106], as the standard method for diagnosis of GDM for more than two decades.

In 2008, the HAPO study [39] demonstrated presence of unfavourable neonatal outcomes even in those with mild hyperglycaemia which did not meet the old criteria of GDM [107]. Based on this notion the International Association of Diabetes and Pregnancy Study Group (IADPSG) recommended a one-step 75 g OGTT testing but lowered the diagnostic cut-point of the OGTT to (5.1–10.0-8.5 mmol/L, fasting, 1-hour and 2 hours postprandial) in 2010 [108] and only one abnormal value was enough to make a diagnosis. This was adopted by ADA [109], WHO [110] and FIGO [111] by recommending a one-step 75 g glucose OGTT between 24 and 28 gestational weeks and diagnosis of GDM is made with only one abnormal value equal to or exceeding 5.1–10.0-8.5 mmol/L, due to the result of the HAPO study regarding mild hyperglycaemia and adverse clinical outcome, including LGA, primary caesarean, clinical neonatal hypoglycaemia, and C-protein cord blood [108] where a more strict strategy may help reduce the frequency of these potential complications. However, several guidelines including the ACOG [112], NIH [113] and SOGC [114] did not support the IADPSG criteria and their guidelines still recommend the two-step strategy and the C-C or NDDG criteria for the OGTT, the reasons provided are:


Current ADA guidelines recommended selective screening of high risk women for GDM, where ACOG guideline advice universal screening and NICE guideline recommended screening all women of South Asians ethnicity. In the HAPO study risk of adverse outcomes were very low when FPG was ≤4.4 mmol/L (80 mg/dl). In Chinese women with FPG value ≥5.1 mmol/L, one can make a diagnosis of GDM (specificity 100% and, in those with value ≤4.4 mmol/L one can exclude GDM (87.8%, sensitivity). These results are similar to those reported by Agarwal, et al. in the HAPO cohort. In HAPO and two other studies, the incidence of selected adverse maternal and fetal outcomes increases along a continuum of increasing maternal hyperglycaemia, with no outcome-associated glycaemic thresholds were identified that could be used to define internationally accepted criteria for the diagnosis of GDM. In 2010, IADPSG [108] consensus panel using HAPO study primary outcomes (birthweight >90%, primary caesarean section rate, neonatal hypoglycaemia and cord C-peptide levels >90%) and threshold for 75-g OGTT

reached odds ratio 1.75. These arbitrary thresholds, when applied to the HAPO cohorts, led to a GDM incidence of 17.8%. In 2013 Canadian Diabetic Association expert committee conceded the dispute and chosen sequential screening with a 50 g GCT followed by 75 g OGTT using the glucose thresholds that result in an Odds Ratio (OR) of 2.00 (fasting ≥5.3 mmol/L, 1 hour ≥10.6 mmol/L, 2 hours ≥9.0 mmol/L).

use. In such instances, clinicians should continue using glucose measurements for

a. First, some haemoglobin traits, such as HbS, HbC, HbF, and HbE, interfere

A1c assay may not be reliable under the underlisted conditions [115]

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation…*

with some A1c assay method. These are common among blacks

b. Second, conditions causing changes in red cell turnover: haemolytic anaemias, chronic malaria, major blood loss, or blood transfusions,

c. Third, A1c levels appear to increase with age [116], though this is not

d. Similarly, racial disparities in A1c, the etiology and significance are unclear

e. Finally, in rapidly evolving type 1 diabetes, no time to "catch-up" with the sudden elevations in glucose levels; diagnosis should be relied on plasma

The glycated haemoglobin (HbA1c) test has been suggested as an alternative screening test for type 2 diabetes. HbA1c overcomes many of these difficulties as fasting state is not required, analytical variability is less than 2% and gives

glycaemic status over past 2–3 month. The coefficient of variation is usually 2–3% for the same day analysis, while the inter-assay variation is 4–5%. HbA1c values are relatively stable after collection, and the recent introduction of a new reference method to calibrate all HbA1c assay instruments should further improves HbA1c

Regrettably, at variance with that report, the New Hoorn Study [118] showed that 44% of people with newly diagnosed diabetes with OGTT had A1c < 6.0% and that a stronger correlations between plasma glucose and A1c is better in subjects with known diabetes, but not in the general population. Moreover, in the Rancho Bernardo Study [119], 85% of the participants with A1c ≥6.5% were not classified as diabetes by ADA criteria and a 1/3rd of people with diabetes on OGTT had A1c

2. Better summary of overall glycaemic exposure and risk for long-term complications

*The beauty of A1c testing compared to blood glucose for diagnose of diabetes mellitus.*

5. Relatively unaffected by acute(eg stress or illness related) perturbations in glucose levels

glucose in association with typical symptoms

a. better indicator of overall glycemic exposure

b. less variability, unaffected by outside factors like stress

c. not a timed test, requires no fasting; more convenient

both diagnosis and monitoring of diabetes.

*DOI: http://dx.doi.org/10.5772/intechopen.96549*

sufficiently clear

[117]

assay standardization.

Advantages of HbA1c assay are:

d. Better at predicting complications

1. Assay is normalized and aligned to the DCCT/UKPDS

6.Currently used to guide management and adjust therapy

3. It has significantly less biologic fluctuation 4. No need for fasting or timed samples

**Table 13.**

**139**

Hyperglycaemia first detected at any time during pregnancy should be classified as either:


When glucose abnormalities persist postpartum in a woman with GDM, her diabetes is re-categorized as overt diabetes, especially if the diagnosis of GDM occurred before 20 weeks' gestation and glucose levels were markedly elevated in pregnancy. The 2006 WHO criteria should be used in diagnosis of Diabetes mellitus in pregnancy when one or more of the following criteria are met:


The diagnosis of GDM at any time during pregnancy should be based on any one of the following values:


There are no established criteria for the diagnosis of diabetes based on the 1-hour post-load value. At least one of these thresholds must be equaled or exceeded to make a diagnosis of GDM.
